Psychophysical and electrophysiological experiments are planned to study the influence of selected visual exposure and deprivation on development of the visual system. Human subjects who have imposed orientation-specific deprivation as a result of ocular astigmatism will be tested to determine levels of visual disfunction. Kittens will be reared with deprived vision or imposed conditions of visual imbalance and then single cells in the visual cortex will be studied to determine the effects of the procedures.